Investment Securities - Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Investments, Debt and Equity Securities [Abstract]
Held-to-maturity, amortized cost, one year or less	$ 1,940
Held-to-maturity, amortized cost, after one through five years	88,294
Held-to-maturity, amortized cost, after five through ten years	381,912
Held-to-maturity, amortized cost, after ten years	2,098,454
Held-to-maturity, amortized cost, securities not due on a single maturity date	1,048,170
Amortized Cost	3,618,770	$ 3,639,850
Held-to-maturity, fair value, one year or less	1,936
Held-to-maturity, fair value, after one through five years	83,044
Held-to-maturity, fair value, after five through ten years	337,841
Held-to-maturity, fair value, after ten years	1,569,609
Held-to-maturity, fair value, securities not due on a single maturity date	937,195
Held-to-maturity, fair value, total	2,929,625	2,949,951
Available-for-sale, amortized cost, one year or less	4,510
Available-for-sale, amortized cost, after one through five years	107,184
Available-for-sale, amortized cost, after five through ten years	193,731
Available-for-sale, amortized cost, after ten years	1,014,687
Available-for-sale, amortized cost, securities not due on a single maturity date	1,508,611
Available-for-sale, amortized cost, other securities (no maturity)	217
Amortized Cost	2,828,940	2,852,774
Available-for-sale, fair value, one year or less	4,480
Available-for-sale, fair value, after one through five years	106,936
Available-for-sale, fair value, after five through ten years	182,383
Available-for-sale, fair value, after ten years	816,920
Available-for-sale, fair value, securities not due on a single maturity date	1,380,913
Available-for-sale, fair value, other securities (no maturity)	217
Available-for-sale, fair value, total	$ 2,491,849	$ 2,529,426